Medium-chain triglyceride (MCT) oil is a popular supplement, primarily known for its rapid energy source when ingested. Derived from coconut or palm kernel oil, it is a purified fat used in many health and wellness routines. When applied to the skin, the question arises about its ability to pass this protective barrier. The unique molecular structure of MCTs allows for a degree of transdermal absorption.
Defining Medium-Chain Triglycerides
MCT oil is distinct from conventional dietary fats due to its specific chemical makeup. Most dietary fats are long-chain triglycerides (LCTs), containing fatty acids with 13 to 21 carbon atoms. MCTs, in contrast, are composed of shorter fatty acids, typically ranging from 6 to 12 carbon atoms.
The most common components in commercial MCT oil are caprylic acid (C8) and capric acid (C10). These are isolated from source oils, such as coconut oil, through fractionation. The short length of these fatty acid chains is the fundamental reason for the oil’s unique metabolic properties and its capacity for skin penetration.
The Science of Transdermal Absorption
The skin’s primary defense against foreign substances is the stratum corneum, the outermost layer often described as a “brick and mortar” structure. This layer is composed of dead skin cells embedded in a lipid matrix. For a molecule to be absorbed transdermally, it must navigate this lipid-rich barrier, governed largely by its size and fat solubility.
The guideline for passive diffusion through the skin is the “500 Dalton rule,” suggesting that molecules with a molecular weight under 500 Daltons are more likely to penetrate the stratum corneum. The fatty acids that make up MCTs (C8 and C10) have molecular weights significantly below this threshold, giving them an inherent advantage over bulkier LCTs. Their high lipophilicity, or fat-loving nature, allows them to readily dissolve into and pass through the lipid matrix of the skin barrier.
While transdermal absorption occurs, the volume and depth are generally limited. The skin remains an effective barrier, meaning only a small fraction of the applied oil will fully cross the epidermal layers and enter systemic circulation. For this reason, MCTs are sometimes used in pharmaceutical formulations as “penetration enhancers” to help deliver other fat-soluble compounds into the skin.
Practical Uses for Topical MCT Oil
The absorption potential of MCT oil translates into several practical applications in skincare and cosmetic formulations. As an emollient, it creates a lightweight, non-greasy film on the skin’s surface that traps moisture. This action helps maintain the skin’s natural hydration barrier, reducing dryness and flakiness.
MCT oil is also non-comedogenic, meaning it is less likely to clog pores compared to many other oils. This characteristic makes it a suitable moisturizer for various skin types, including those prone to acne or sensitivity.
The oil is widely used as a carrier oil in aromatherapy and cosmetic products. Its ability to penetrate the upper layers of the skin efficiently and its high stability against oxidation make it an effective vehicle for delivering other fat-soluble active ingredients. When mixed with essential oils or certain vitamins, MCT oil helps transport these compounds deeper into the epidermis. This role as a carrier in topical preparations is one of its most significant commercial applications.
Metabolic Fate of Absorbed MCTs
Once the limited quantity of MCTs passes through the skin barrier and enters the bloodstream, their metabolic fate is unique compared to LCTs. When absorbed, MCTs are not primarily packaged into large transport molecules called chylomicrons, as long-chain fats are.
Instead, medium-chain fatty acids are transported directly to the liver via the portal vein. In the liver, they undergo rapid beta-oxidation, converting the fatty acids quickly into energy. They do not require the carnitine transport system necessary for LCTs to enter the cell’s energy-producing mitochondria.
This rapid processing means the absorbed MCTs are quickly converted into ketone bodies, which serve as an immediate source of fuel. Consequently, they are less likely to be stored as body fat. This metabolic efficiency ensures that any small amount absorbed through the skin is efficiently utilized by the body, mirroring the process that occurs when MCT oil is consumed orally.